One of the problems of drug abuse facing the scientific community concerns keeping abreast with the appearance of new compounds subject to illicit use. The last six years have shown a steady increase in the abuse of a new psychotomimetic phencyclidine (PCP). Originally developed as an anesthetic, this compound is now often found as the sole ingredient or as an adulterant in street samples of drugs sold as mescaline or tetrahydrocannabinol, although there is evidence that PCP is being abused as the drug of choice in an increasing number of users. We propose to study the behavioral pharmacology of PCP in two species of non-human primates. In squirrel monkeys we will be studying the effect of this compound on schedule-controlled operant behavior; we will investigate the possibility of tolerance and physical dependence development. We will also consider the interaction of PCP with other drugs of abuse. We propose to extend previous work on the intravenous self-administration of PCP to study the pattern of drug intake and the toxicity associated with unlimited access to the drug by rhesus monkeys. In addition, self-administration procedures will be used to study the abuse liability of a structurally and pharmacologically related compound, ketamine, and possibly other members of the series such as the thiophene analog of PCP.